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BTU
Understanding of soil carbon dynamics after establishment of alley-cropping systems is crucial for mitigation of greenhouse gas CO2. This study investigates soil CO2 flux in an alley-cropping system composed of black locust (Robinia pseudoacacia L.) and poplar (Max 1) tree strips and adjacent to them crop strips (Lupinus/ Solarigol). Soil CO2 flux was measured monthly over the March – November 2012 period, using a LI-COR LI-8100A automated device. Simultaneously with CO2 flux measurements, soil and air temperature, soil moisture, microbial C and hot water-extractable carbon (HWC) were determined for soils collected nearby each measurement collar. Root biomass was measured to a depth of 15 cm. In all sampling areas, soil CO2 flux increased from May to July, showing a significant positive correlation with air and soil temperature, which can be a reflection of increase in photosynthetic activity over the warm summer months. The relationships between soil moisture and CO2 flux showed positive correlation only for the warm period (May - October), indicating enhancing role of soil moisture on microbial mineralization and root respiration. CO2 flux values varied between sampling areas at different vegetation periods, with significantly higher values in trees over the summer. This could be attributed to the higher photosynthetic activity and higher root density in trees coppices compared to crops. In autumn, after seeding catch crop mix Solarigol, CO2 flux was significantly higher in crops compared to trees, which could be related to soil tillage prior to seeding of crops, as well as to the higher photosynthetic activity of newly seeded crops at the period of rapid plant growth. Despite a seasonal variation in CO2 flux between sampling areas, aaverage CO2 flux values observed over March – November period did not differ significantly between sampling areas, showing 2.5, 3.2, and 2.9 μmol m-2 s-1 values for black locust, poplar and crops, respectively. A greater C loss with soil respiration under trees in summer period may be compensated by greater C assimilation and storage in woody biomass, and the greater respiration from crop strips after tillage in autumn.
The production of energy wood on arable land increased in Germany during the last years. Black locust (Robinia pseudoacacia L.) is a suitable tree species in order to ensure substantial woody biomass yields on agricultural sites in eastern Germany. Arranged in hedge structures (alley cropping) positive effects on wind velocity and hence on soil erosion can be expected for the whole agricultural production area.
Results of field measurements carried out in several alley cropping sites located in eastern Germany show that wind velocity can be reduced by more than 50 %, even though tree hedgerows were not higher than four meters. Here, the reduction of wind speed was dependent on the distance to woody crops, the width of the crop alleys and the orientation of hedgerows. As a result of wind speeds reduction the potential of soil erosion by wind decreases considerably. The risk of wind erosion is even nearly negligible for 24 m wide or smaller crop alleys.
The establishment of short rotation hedgerows could contribute to an enhanced protection against wind erosion and thus to an ecological and possible long-term economic appreciation of agricultural sites. Aside from erosion control, further advantages such as a lower evaporation rate, and thus a crop yield increase, may be connected to the establishment of such agroforestry systems. Against the background of the increasing demand for woody biomass for bioenergy, the cultivation of fast growing trees on agricultural sites can furthermore result in an additional incomefor farmers. This is a prerequisite for the spread of this kind of agroforestry in Germany, because a comparable large share of an unprotected field has to be planted with trees in order to ensure an efficient windbreak.
Die Agroforstwirtschaft, also die kombinierte Nutzung von Bäumen und Feldfrüchten auf einer landwirtschaftlichen Fläche, gewinnt vor dem Hintergrund der steigenden Holznachfrage sowie diverser ökologischer Vorteilswirkungen auch in Deutschland
zunehmend an Bedeutung. Verglichen mit den bereits bekannten Umweltleistungen, wie etwa einer erhöhten Biodiversität sowie dem Schutz vor Winderosion, ist der potenzielle Einfluss der Gehölzstreifen auf das Wachstum bzw. die Nährstoffversorgung von angrenzenden Feldfrüchten in Agroforstsystemen noch weitestgehend ungeklärt. Zur Quantifizierung dieser möglichen Interaktion wurden im Jahr 2013 auf einem etwa 40 ha großen Agroforst-Versuchsstandort nahe der Stadt Forst (Lausitz) umfangreiche Nährstoff- und Ertragsuntersuchungen durchgeführt.
ln der Region Südbrandenburg herrschen ertragsschwache, sandige Böden vor, die von Natur aus ein geringes Wasserhaltevermögen und ein hohes Degradationspotential durch Winderosion aufweisen. Zudem existiert hier ein
vergleichsweise großer Flächenanteil an strukturarmen, großflächigen Bergbaufolgelandschaften, die sich zume1st durch eine geringe Standortsgüte auszeichnen. In diesem Beitrag werden Ergebnisse aus versChiedenen Studien vorgestellt, in denen untersucht wurde, ob und in welchem Ausmaß durch im Kurzumtrieb bewirtschaftete Agroforstsysteme die Anfälligkeit dieser Ackerstandorte gegenüber Winderosion gemindert und die im Boden bzw. Kippensubstrat vorhandene Menge an organischer Substanz erhöht werden kann.